Proximal notification is a method by which a device, human or object is notified when another device, human or object is in certain range of another. For example, a user's GPS-enabled phone could data to the server at regular intervals. These points would be used used to create an accurate, real-time map that the other party could easily see. The system would then be able to detect when two people are a certain distance of one another. When the two users are a certain distance apart, an SMS or Push notification message could sent to both parties.
Proximal notification is a useful feature in reducing the friction of everyday life and the uncertainty of meeting someone. Instead of waiting for someone, a person can wrap up client work or finish what they are doing right up until the moment the other party gets there. It’s the equivalent of “on my way” and “here”, the two most common co-location ‘drags’.